The invention relates to a cylinder head for a two-stage reciprocating piston compressor which includes an intercooler that is designed as a cooled overflow channel between the pressure side of the first stage and the suction side of the second stage, wherein the overflow channel has a substantially slot-like cross-section, and wherein the overflow channel is in addition divided by at least one indirectly cooled center rib so that therefrom at least two overflow channel portions are created.
Today, commercial vehicles such as, for example, trucks, busses, construction machines and rail vehicles, have in most cases brakes which are actuated with the support of compressed air, and for the compressed-air supply usually a compressor is provided which is driven by the internal combustion engine that serves for driving the vehicle. Such a compressor often also supplies compressed air to further sub-systems of the vehicle such as, for example, the pneumatic suspension. The cylinder head of this compressor comprises the suction and pressure valves including the associated feed and discharge channels, and is today in most cases integrated at least in the cooling circuit of the internal combustion engine, so that even if the compressor runs at a high speed level for a longer period of time, or if high compressor capacity is required for a longer period of time, the temperature level of the compressor can be kept adequately low. Thus, temperature problems mainly occur in the pressurized gas which, in the case of two-stage reciprocating piston compressors, should preferably be cooled not only at the outlet of the reciprocating piston compressor, but should already be cooled without any losses prior to entering into the second compressor stage so that the occurring maximum temperatures of the gas do not exceed a given value. Furthermore, an inlet gas temperature that is lower with regard to the second compressor stage results in an increased compressor capacity.
The suctioned ambient air is usually guided via the suction tube of the first stage into the suction chamber thereof. After a working stroke of the piston of the first stage, the air arrives as pressurized gas via the pressure valve in the pressure chamber of the first stage. Via an intercooler designed as a cooled overflow channel between the pressure side of the first stage and the suction side of the second stage, the pressurized gas is fed into the suction chamber of the second stage and, after this double compression, exits the reciprocating piston compressor. Such intercoolers in different embodiments have been known for a long time, wherein, however, mostly separately cooled wall elements or the like are used.
From DE 10 2005 012 202 A1, a cylinder head of the aforementioned type is known in which the pressure chamber of the first stage and the suction chamber of the second stage are combined so as to form a intermediate chamber with water-cooled ribs. In the preferred embodiment, these water-cooled ribs are implemented as cast parts. Another configuration provides the use of a formed sheet metal part that forms the water-cooled ribs. Both variants provide that each of the ribs is water-cooled. Since the cooling-water-carrying cross-section of the ribs cannot be reduced at will in order to avoid a stalling flow and increased friction in the cooling water, there is only a greatly reduced volume available for the compressed air to be cooled, due to the limited constructed space in the cylinder head. Thus, for this reason, the heat transfer from the pressurized gas into the cylinder cooling system of the known embodiment cannot be optimized further.
DE 2905720 A1 shows a cylinder head for at least two-stage compressors, in which cylinder head the flow channel between the pressure side of the first stage and the suction side of the second stage is configured as an intercooler in such a manner that said overflow channel is surrounded by a coolant chamber. As a further measure for dissipating head, ribs are provided which protrude into the low-pressure chamber and through which no coolant flows. Since the additional ribs are arranged directly above the pressure valve of the first stage, a further increase in cooling capacity, for example by elongating the ribs or increasing the cooling surface in a different way, is not possible.
It is an object of the present invention to design a cylinder head of the aforementioned type in such a manner that the mentioned disadvantages of the known embodiment are avoided, and that in particular the cooling effect on the pressurized gas between the two stages can be improved while maintaining a simple production possibility.